A sewer flood control system for a building requires a pit or hole which extends from ground level to below the sewer pipe connecting the building to the public sewer system. Heavy equipment is frequently used to dig the pit or hole. The use of such heavy equipment results in considerable destruction of the landscaping around the area of the pit or hole, and also of the path used to move the heavy equipment between the street and the location of the pit or hole between the building and the street. The pit or hole must be lined, and again heavy equipment has been used to lower a concrete liner or vault into the pit or hole. The hole dug to receive the concrete vault must be considerably larger in diameter than the outside dimensions of the vault, typically a 60 inch diameter hole for a 48 inch diameter vault.
It has been found desirable to be able to install vaults in pits or holes of various depths without the need for heavy equipment to dig the hole for the vault and to install a waterproof vault. By digging the hole for a vault by hand, the damage done to the landscaping by the movement of and use of heavy equipment to dig the hole is avoided. If a pit is dug by hand, and the vault is constructed of a light weight material, a 48 inch inside diameter vault requires only a 50 to 52 inch diameter hole. Considerably less dirt is removed in digging the pit, thus providing savings with respect to both the digging and the hauling away of the removed material. Further, by forming the vault of a light weight material, which can be carried to the hole by hand, the use of heavy equipment is further avoided.
Federal laws now require the separation of contaminated sewer water from relatively clean storm or rainwater. Therefore the vault must be formed with sealed joints, to prevent infiltration of clean storm or rainwater into the vault, or the outward flow or filtration of contaminated sewer water.
While shoring is not required while digging a hole with heavy equipment, when a hole is dug by hand, with workers in the hole, OSHA rules require cave in protection when the depth of the hole exceeds 4 feet. Thus, it is desirable to form the vault with vertical sections of light weight material, which can be lowered into the hole as the depth of the hole is increased, thus providing the OSHA required shoring. However, some jurisdictions in implementing the OSHA requirement my require a shoring structure separate from the vault, inside of which the vault is placed. In which case, it is desireable to form both the shoring structure and the vault with vertical sections of light weight material.